Many wild plants form below-ground associations with fungi, exchanging the products of photosynthesis for increased access to soil nutrients and water, as well as a range of other benefits. Mycorrhizal fungi are often present in agricultural soils also, but we usually don't account for them in farm management. But if plants can benefit from these associations, shouldn't we consider the potential that they affect crop yield?
I'm in the middle of my first foray into visualizing one type of these fungi, the ericoid mycorrhizal species found on blueberry roots. In the picture here, you can see coils of blue-gray fungal hyphae inside the cortical cells of blueberry roots from a farm in northern Vermont. The color is not natural: to visualize these structures you have to bleach out the root's color, then stain the fungi.
Why are these things worth visualizing? In an ongoing experiment (more on this soon), I have found that when I actively inoculate blueberry plants with ericoid mycorrhizal fungi, they behave differently, growing larger leaves and longer flowers, and becoming less appealing to herbivores. There is also some suggestion that inoculated plants make larger fruit, meaning that farmers could realize a long-term benefit from an investment in fungus at planting time.